This project is part of a long-term study of the behavior and ecology of rain-forest monkeys in the Kibale Forest of Uganda, East Africa. Seven species of monkeys live in this forest and studies have been completed on 3 of these. Studies on 2 other species, blue monkey (Cercopithecus mitis) and red tail monkey (Cercopithecus ascanius), are in progress. The approach is essentially comparative. At least 5 species will be studied in one and the same section of forest and later some of these species will be studied in other forest types within the same forest reserve. Study of the 5 species in the same place emphasizes the problems of ecological niche separation and the relation between ecology and social behavior, such as group size and composition, inter-individual distance, frequency of social behaviors, intergroup relations, etc. Study of the same species in different habitats is aimed at understanding the effects of differences in tree composition and structure of the forest on ecology (time budget, home range size and ranging patterns) and social behavior (group size and composition and intergroup relations).